It is known to use adjustable coverings over architectural openings. Such adjustable coverings include cellular panels, Venetian blinds, and many other systems for controlling the passage of light, vision, or air through the architectural openings. For example, cellular panels and Venetian blinds can be adjusted by retracting or extending them, and Venetian blinds may be further adjusted by tilting the slats comprising part of the blind.
Tilter mechanisms for Venetian blinds have been created in a variety of configurations. One such tilter mechanism is described in U.S. Pat. No. 5,341,865 "Fraser et al.", which is hereby incorporated by reference. As shown therein, a tilter mechanism typically includes a tilt drum (also called a "tilt roll") that is co-axially mounted on an elongated tilt rod and is adapted to receive the forward and rear ladder laces of the Venetian blind. When the tilt rod is rotated, it rotates the drum in unison therewith, which wraps one of the ladder laces and unwraps the other, thereby causing the slats of the Venetian blind to tilt open and closed about longitudinal/horizontal axes. The tilt rod (and drum) can be rotated by a variety of tilters, including by gear mechanisms driven by a remotely controlled motor or by the manual force of the Venetian-blind user. Tilter mechanisms are also employed to effect adjustment of other adjustable coverings for architectural openings.
In a Venetian blind, the tilter, tilt drum, and tilt rod are all generally located within the headrail housing of the blind (along with other mechanisms such as pulleys and locks to facilitate lifting of the blind). Tilt drum supports are also fixedly attached to the headrail housing to support the tilt drums and/or tilt rod along the length of the headrail. The tilt drum supports prevent the tilt rod from sagging due to the weight of the blind and generally prevent axial movement of the tilt drums relative to the headrail housing.
It is desirable that the tilt rod not be permitted to move axially within the headrail housing. If the tilt rod becomes dislodged from the tilter, for example, the blind cannot be tilted. Moreover, if the tilt rod slides axially within the headrail, it can interfere with other mechanisms, such as the lock for the blind's lifting mechanism. To avoid these problems, the tilt rod can be held in place by a tight connection to the tilter; however, providing a tight fit in the tilter has been found to be cumbersome and difficult during assembly of the blind. Accordingly, the tilt rod is often manufactured in polygonal cross-section that can be slid into a mating, but not tight-fitting, connection in the tilter.
The tilt rod is then held laterally in place by tight fitting connection to the tilt drum. A tight fit between the tilt drum and tilt rod prevents the drum from accidentally sliding relative to the tilt rod. Moreover, because the tilt drums are prohibited from moving laterally by fixed tilt drum supports, the tilt rod can be kept in place without requiring a tight connection to the tilter.
Generally, at least one-half pound of force of interference fit is required between the drum and the tilt rod. Due to manufacturing tolerances, however, the interference-fit force of prior art tilt drums on the tilt rod may be as much as four pounds or more. A high interference-fit force can make it frustrating and difficult to assemble the tilt drum onto the tilt rod.